US5088965A - Radial tensioner - Google Patents

Abstract

A tensioning device is provided for selecting and imparting torsional bias to a shaft and simultaneously providing a shock absorbing mechanism. The device includes a resilient elastomeric biasing member in the form of a web extending radially between the shaft and an actuator member. The first end of the biasing member is connected to the shaft for conjoint rotation therewith and the second end of the biasing member is connected to the actuator member. A locking mechanism selectively connects the actuator member to a fixed frame after a torsional biasing force is imparted to the shaft.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a tensioning device which is used to select and impart a moment of torque to a shaft. The present tensioning device has been found to be particularly useful in connection with conveyor belt cleaners which utilize scraper blades to clean a conveyor belt. Conveyor belt scraper blades are conventionally mounted on a shaft which is positioned transverse to the direction of conveyor belt travel. When the shaft is rotated, the blades are forced into contact with the belt to scrape off adherent material. Over time the scraper blades wear and lose contact with the belt thereby hampering the blades cleaning ability. The shaft on which the scraper blades are mounted must then be rotated to reposition the scraper blades against the belt with the desired amount of force.

Conveyor belt scraper blades are subjected to repeated impact forces which are generated by the blades coming into contact with conveyor belt splices, with enlarged pieces of the conveyed material, or other debris which adheres to the belt, all of which can cause appreciable damage to the scraper blades or the conveyor belt cleaning mechanism. To promote effective cleaning of the conveyor belt and to avoid shutting the belt down for repair, it is of the utmost importance to provide the scraper blades with a shock absorbing capability.

Previous torsional tensioning devices of the types shown in U.S. Pat. No. 4,533,036 and 4,925,434 and in U.S. patent application Ser. No. 561,969, filed Aug. 2, 1990 entitled "Spring Steel Tensioner" have been used in connection with conveyor belt scraper blades. In these devices the biasing means extends in a generally linear direction which is substantially parallel and concentric to the central axis of the conveyor belt cleaner shaft. In each of these devices the biasing means is torsionally rotated such that one end of the biasing means is rotated about the longitudinal axis of the biasing means with respect to the other end of the biasing means. In other words, the biasing means is twisted about its central longitudinal axis. A torsional force is thereby created and stored within the biasing means which provides the torsional biasing force to rotate the cleaner shaft. In each of these devices the torsional force which is applied to the tensioner by the user equals the torsional force generated in the biasing means and in the shaft. The torsional force in the biasing means can not be varied without affecting the torsional force applied to the shaft. Torsional springs used for mounting a conveyor belt cleaner to a shaft are shown in U.S. Pat. Nos. 3,674,131 and 4,533,035. A torsion spring is also shown in U.S. Pat. No. 4,171,920.

SUMMARY OF THE INVENTION

The present invention provides a tensioning device which is particularly useful in biasing conveyor belt scraper blades, which are mounted on a rotatable shaft, into contact with a conveyor belt. The tensioning device includes a biasing member consisting of a resilient elastomeric web having a first end, a second end and a center section extending radially between the first end and the second end. The first end of the biasing member is connected to the shaft and the second end of the biasing member is connected to an actuator member which is selectively rotatable within a base which is attached to a fixed frame such as a conveyor chute. The biasing member extends radially outwardly from the shaft to the actuator member such that appropriate rotation of the actuator member will create a biasing force in the biasing member.

The actuator member is selectively connectable to and relatively repositionable with respect to the fixed frame. As the actuator member is repositioned, a biasing force will be created and stored within the biasing means much the same as winding the spring of a watch stores a force. The biasing means applies a torsional biasing moment to the shaft for rotation thereof. The magnitude of the biasing force within the biasing means may be adjusted while maintaining the same torsional biasing moment which is applied to the shaft. The magnitude of the torsional biasing moment which the biasing member is able to provide for the rotation of the shaft can be adjusted by changing the cross sectional dimensions of the biasing member, by using various different materials for the biasing member, or by repositioning the actuator member relative to the fixed frame. An infinite range of torques may be selected and applied to the shaft by repositioning the actuator member with respect to the mounting frame at various distances as desired. The biasing member provides a shock absorbing mechanism for the scraper blades such that shocks which normally would be transferred from the shaft to the mounting frame will instead be absorbed, at least in part, by the biasing member.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the radial tensioning device shown installed in a conveyor chute.

FIG. 2 is a cross sectional view of the radial tensioning device.

FIG. 3 is a cross sectional view of the radial tensioning device taken alonglines 3--3 of FIG. 2.

FIG. 4 is an exploded perspective view of the radial tensioning device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a radial tensioning device generally designated with thenumeral 10 fastened to aconveyor chute 12. A plurality ofscraper blades 14 are removably secured to ashaft 16 which extends transversely to the direction of travel of aconveyor belt 18 as illustrated and described in U.S. Pat. No. 4,643,293 owned by Martin Engineering Company. Thescraper blades 14 may be moved into or out of scraping engagement with theconveyor belt 18 by the appropriate rotation of theshaft 16 about itslongitudinal axis 20. Theshaft 16 extends between afirst end 22 best illustrated in FIG. 2 and a second end not shown. Thetensioner 10 is shown in FIG. 1 in use with a secondary cleaner, however, thetensioner 10 may also be used with primary cleaners and other types of devices which require tensioning.

Theradial tensioner 10 includes abase 24 having amounting plate 26 and asleeve 28. Themounting plate 26 includes anouter surface 30 located adjacent to thechute 12 and aninner surface 32. Themounting plate 26 includes acentral aperture 34 and four apertures 36 A-D. Thesleeve 28 is generally circular in cross-section and includes a generally circularouter wall 38 and a circularinner wall 40. Thesleeve 28 extends from themounting plate 26 and terminates in arim 42. Ahollow chamber 44 is formed within thebase 24 by theinner wall 40 of thesleeve 28 and theinner surface 32 of themounting plate 26. Thesleeve 28 also includes fourribs 46A-D best seen in FIG. 4 which extend from theouter wall 38 such that thesleeve 28 is thicker at each rib 46. A threadedaperture 48 extends through eachrib 46A and 46B. A threadedaperture 50 extends through eachrib 46C and 46D of thesleeve 28. The threadedapertures 48 are located in thesleeve 28 in a position which is closer to themounting plate 26 than are the threadedapertures 50. Aset screw 52 is threadably inserted into eachaperture 48. Astop bolt 54 is inserted through awasher 56 and into eachrespective aperture 50. Thebase 24 is rigidly mounted to thechute wall 12 byfasteners 58 which extend through theapertures 36A-D of themounting plate 26.

Thetensioner 10 also includes anactuator member 60 which includes ahub 62 and ahexagonal end 64. Thehub 62 includes asidewall 66 having a cylindricalinner surface 68 and a generally cylindricalouter surface 70. Thehub 62 also includes abackwall 72 having aninterior surface 74 and anouter surface 76. Thesidewall 66 extends from thebackwall 72 and terminates in arim 78. Thesidewall 66 and thebackwall 72 form ahollow chamber 80 within theactuator member 60. Thehexagonal end 64 extends outwardly from theouter surface 76 of thebackwall 72. Twogrooves 82A and 82B are formed in theouter surface 70 of thesidewall 66. Eachgroove 82A-B extends around the circumference of thesidewall 66. Eachgroove 82A-B is formed by a pair ofsidewalls 84 and a bottom wall 86. Agroove 88 is also formed in theouter surface 70 of thesidewall 66. Thegroove 88 is located between thegrooves 82A and 82B and also extends around the circumference of thesidewall 66. Thegroove 88 is formed by a pair ofsidewalls 90 and abottom wall 92. Thegrooves 88 and 82A form arib 93 therebetween in thesidewall 66 of theactuator member 60. Abearing 94 is located within eachgroove 82A and 82B. Each bearing 94 includes ananti-friction surface 96 which extends a distance outwardly from theouter surface 70 of thesidewall 66. Thebearings 94 are preferably strips of an anti-friction material such as ultra-high molecular weight polyethylene. Other anti-friction bearing means may be used as desired. Theactuator member 60 also includes aslot 98 which extends through thesidewall 66 of thehub 62. Theslot 98 is formed by acircular aperture 100 and an adjoining generallyrectangular aperture 102. Thecircular aperture 100 extends through thegroove 82B and through a portion of thegroove 88.

Theactuator member 60 is located within thebase 24 such that therim 78 of thesidewall 66 is in close proximity to theinner surface 32 of the mountingplate 26 and such that the anti-friction surfaces 96 of thebearings 94 are in contact with theinner wall 40 of thesleeve 28. Thegroove 82A and itsbearing 94 are located near therim 78 of thehub 62 while thegroove 82B and itsbearing 94 are located near therim 42 of thebase 24. Thegroove 88 is located on thesidewall 66 of thehub 62 such that it aligns with the threadedapertures 50 and thestop bolts 54. Therib 93 on thehub 62 is located such that it is aligned with the threadedapertures 48 and the set screws 52. Thesidewall 66 of thehub 62 may have various different diameters as desired. Theactuator member 60 is rotatable within thebase 24 and is selectively connectable to the base 24 with theset screws 52 such that theactuator member 60 may be selectively rigidly connected to thebase 24 and to thechute 12.

Theactuator member 60 may also include abushing 104 having a circularouter wall 106 and a circularinner wall 108 defining abore 110. Thebore 110 extends from afirst end 112 of thebushing 104 through asecond end 114. Thefirst end 112 of thebushing 104 is located at therim 78 of thehub 62 and thesecond end 114 is located at the location where therectangular aperture 102 joins thecircular aperture 100 in thehub 62. Theouter wall 106 of thebushing 104 is of a sufficient diameter to fit closely within theinner surface 68 of thehub 62. Thebushing 104 may be made of various different materials, however, 60 Shore A rubber is preferred. Although it is preferred to include thebushing 104 in thetensioner 10, especially when thetensioner 10 is used with a primary cleaner, thebushing 104 may be eliminated if desired.

As best shown in FIG. 2, theradial tensioner 10 may include anadapter 116. Theadapter 116 extends between afirst end 118 and asecond end 120. Theadapter 116 includes afirst sleeve 122 and asecond sleeve 124. Thefirst sleeve 122 includes a circularouter wall 126 and a circularinner wall 128 which defines abore 130 extending through thefirst sleeve 122. Thefirst sleeve 122 extends from thefirst end 118 of theadapter 116 to asecond end 132. Thesecond sleeve 124 includes a circularouter wall 134 and a circularinner wall 136 which defines abore 138 which extends through thesecond sleeve 124. Thesecond sleeve 124 extends from thesecond end 120 of theadapter 116 to afirst end 140 which is located within thebore 130 of thefirst sleeve 122. Thefirst sleeve 122 is rigidly connected to thesecond sleeve 124 by welding or other means. Thefirst sleeve 122 and thesecond sleeve 124 may also be made from a single piece of material. Theadapter 116 includes aslot 142 best shown in FIG. 4 which extends through theouter wall 134 and theinner wall 136 of thesecond sleeve 124. Theslot 142 also extends through thesecond end 120 of theadapter 116. Theadapter 116 also includes two threadedapertures 144 which extend through thefirst sleeve 122. Aset screw 146 is threadably inserted into each threadedaperture 144. The diameter of theouter wall 134 of thesecond sleeve 124 may be varied as desired. As can be seen in FIG. 2, the diameter of thecentral aperture 34 in the mountingplate 26 is slightly larger than the diameter of theouter wall 126 of theadapter 116. Thebore 110 in thebushing 104 is sized to fit securely around theouter wall 134 of thesecond sleeve 124.

Theradial tensioner 10 also includes a biasingmember 148 best illustrated in FIG. 4. The biasingmember 148 consists of a resilient elastomeric web which includes afirst end 150, asecond end 152 and acenter section 154 which extends between thefirst end 150 and thesecond end 152. The biasingmember 148 also extends between afirst side 156 and asecond side 158. Thefirst end 150 of the biasingmember 148 is generally circular in cross-section while thesecond end 152 is generally elliptical in cross-section. The biasingmember 148 is preferably formed of 50 to 60 Shore A ozone resistant natural rubber and is preferably formed of 55 Shore A natural rubber. Thecenter section 154 of the biasingmember 148 extends through therectangular aperture 102 of theslot 98 in theactuator member 60 and through theslot 142 in theadapter 116. Each of theends 150 and 152 of the biasingmember 148 are enlarged relative to the thickness of thecenter section 154 so that they will not be able to pass through therectangular aperture 102 of theslot 98 or theslot 142 in theadapter 116. As can be seen in FIG. 3, the biasingmember 148 extends radially between theadapter 116, which is connected to theshaft 16, and theactuator member 60.

In this application "radially" is to be given the broadest possible interpretation and is meant to include not only a member which extends outwardly in a linear direction but also members which extend in a curvilinear fashion, spirally, or any other form of radial extension wherein thefirst end 150 of the biasingmember 148 is located at a first distance from thelongitudinal axis 20 of theshaft 16 and thesecond end 158 of the biasingmember 148 is located at a greater distance from thelongitudinal axis 20 of theshaft 16. The biasingmember 148 is preferably made of rubber however other materials may be used as desired. It is also envisioned that the biasingmember 148 may take the form of various types of springs which may be made of metal or other materials. More than one biasingmember 148 may also be used with theradial tensioner 10 if desired. While the connection between the biasingmember 148 and theactuator member 60 and theadapter 116 has been shown as utilizing slots, various other means for connecting the biasingmember 148 to theactuator member 60 and theadapter 116 may also be used as desired.

While theradial tensioner 10 has been described herein utilizing anadapter 116 to connect the biasingmember 148 to theshaft 16, theadapter 116 may be eliminated if desired and where conditions allow. When theshaft 16 is of sufficient length and is a hollow tube, theslot 142 may be formed directly in theshaft 16 such that the biasingmember 148 may be attached directly to theshaft 16. When theshaft 16 is solid, other means of connecting the biasingmember 148 directly to theshaft 16 may be used. Theadapter 116 is useful however where theshaft 16 is not of a sufficient length to extend sufficiently into thechamber 80 of thehub 62.

In operation, theadapter 116 is initially inserted over thefirst end 22 of theshaft 16 such that theshaft 16 extends past theapertures 144 in theadapter 116. Theset screws 146 are then turned to secure theshaft 16 to theadapter 116. Thebase 24 is then placed around theadapter 116 such that theadapter 116 extends through theaperture 34 in thebase 24. Thefasteners 58 are then inserted through theapertures 36A-D in the mountingplate 26 to removably secure thetensioner 10 to thechute 12. Thebushing 104 is then placed around thesecond sleeve 124 of theadapter 116. Thefirst end 150 of the biasingmember 148 is inserted into thechamber 80 of theactuator member 60 through thecircular aperture 100 of theslot 98. Theactuator member 60 is then slipped over thesecond end 120 of theadapter 116 and over thebushing 104 while inserting the biasingmember 148 into theslot 142 in theadapter 116. The biasingmember 148 is positioned such that thecenter section 154 of the biasingmember 148 extends through theslot 142, with thefirst end 150 being located within thebore 138 of theadapter 116, and such that thecenter section 154 extends through therectangular aperture 102 of theslot 98, with thesecond end 152 of the biasingmember 148 being located outside of thehub 62. Theactuator member 60 is slipped over theend 120 of theadapter 116 until thegroove 88 is aligned with thestop bolts 54 whereupon thebolts 54 are tightened such that thestop bolts 54 extend into thegrooves 88. Thestop bolts 54 thereby prevent movement of theactuator member 60 in a direction parallel to theaxis 20 while allowing theactuator member 60 to rotate about theaxis 20. Theactuator member 60 is rotatable within thebase 24 and is thereby selectively repositionable with respect to thebase 24 and thechute 12. Rotation of theactuator member 60 within thebase 24 is facilitated by thebearings 94 which are in contact with theinner surface 40 of thebase 24. Theactuator member 60 is selectively connectable to thebase 24 and thechute 12 by the tightening of theset screws 52 down upon therib 93 of theactuator member 60.

In order to bias thescraper blades 14 into engagement with theconveyor belt 18, theset screws 52 are loosened. A common wrench or socket wrench may be used to rotate thehexagonal end 64 of theactuator member 60 which in turn rotates thesecond end 152 of the biasingmember 148. As theactuator member 60 continues to be rotated, the biasingmember 148 will begin to wrap around theouter wall 134 of theadapter 116 until thefirst end 150 of the biasingmember 148 engages theinner wall 136 of theadapter 116. Further rotation of theactuator member 60 will then rotate theadapter 116 and theshaft 16 until thescraper blades 14 come into contact with theconveyor belt 18. Rotation of theactuator member 60 may then be continued to produce the desired moment of torque which will urge thescraping blades 14 against theconveyor belt 18 with the desired amount of force. As theactuator member 60 is rotated with no corresponding rotation of theadapter 116 or theshaft 16, the biasingmember 148 will become elongated thereby creating a tensile biasing force which is stored within the biasingmember 148 and which is applied to theadapter 116 at theouter wall 134 to create a torsional biasing moment on theshaft 16.

The torsional moment applied to thehex end 64 by a user will equal the torsional moment applied to theadapter 116 by the biasingmember 148 and will equal the torsional biasing moment applied to theshaft 16. However, for any given torsional biasing moment applied to theshaft 16, the magnitude of the tensile force within the biasingmember 148, which is needed to generate the given torsional biasing moment, may be adjusted by varying the respective diameters of theouter wall 134 of theadapter 116 and/or of thesidewall 66 of thehub 62. For example, while producing the same torsional biasing moment, the size of the required tensile force within the biasingmember 148 will decrease as the diameter of theouter wall 134 is increased. When the desired amount of tension has been produced in the biasingmember 148 and when the desired torsional biasing moment has been applied to theshaft 16, theset screws 52 are tightened against therib 93 of theactuator member 60, thereby fixing theactuator member 60 against rotation and connecting the actuatingmember 60 to thebase 24 and thechute 12. Theradial tensioner 10 is capable of creating a clockwise or counterclockwise biasing force relative to thelongitudinal axis 20 of theshaft 16 through the appropriate rotation of theactuator member 60.

As thescraper blades 14 wear, the biasingmember 148 will begin to contract thereby causing theshaft 16 to further rotate so that thescraper blades 14 will remain in contact with theconveyor belt 18. Theshaft 16 will continue to rotate as theblades 14 wear until the biasingmember 148 returns to its original non-biased or unstretched position. The biasingmember 148, in either its stretched or unstretched condition, will absorb most rotational forces or shocks that are transmitted from theshaft 16 thereby reducing damage to the conveyor belt cleaner mechanism. Thebushing 104 will additionally absorb any shocks that are transmitted to theshaft 16 by thescraper blades 14 which are substantially linear and perpendicular in direction relative to theshaft 16 to additionally reduce damage to the conveyor belt cleaner mechanism. As can be seen in FIG. 4, the biasingmember 148 may also act to vertically support theadapter 116 and theshaft 16 to thereby relieve the bearing load placed upon thebushing 104 by theshaft 16. While theradial tensioner 10 described herein has been described as utilizing a biasingmember 148 in which a tensile force is created to torsionally bias theshaft 16, biasingmembers 148 in which a compressive or bending force is created within the biasing member are additionally applicable to the present invention.

Thetensioner 10 will limit the backlash forces that may arise when thetensioner 10 is being adjusted while thebelt 18 is in operation or when the direction of rotation of thebelt 18 is reversed. A backlash occurs when thecleaning blades 14 are pulled by thebelt 18 in the direction of rotational bias such that theblades 14 are rotated by thebelt 18 to the opposite side of theshaft 16. Should a backlash occur, as theblades 14 andshaft 16 rotate in the direction of rotational bias, the biasingmember 148 will contract and will unwrap from theadapter 116 thereby limiting the harmful forces which otherwise could be created and applied to thetensioner 10 or thechute 12 during a backlash.

In another embodiment, not shown, the radial tensioner may include a ratchet mechanism consisting of a plurality of teeth (not shown) extending from therim 42 of thebase 24 and a pawl (not shown) pivotally attached to theouter surface 70 of thesidewall 66 of theactuator member 60. The pawl is biased towards therim 42 of the base 24 to engage the teeth in a ratcheting manner preventing rotation of theactuator member 60 in one rotational direction and allowing theactuator member 60 to be rotated in the opposite direction while apply a biasing force upon thehexagonal end 64 of theactuator member 60. As the biasing force is created or increased in the biasingmember 148, the pawl will prevent the biasing force from being lost when the rotational force is removed from thehexagonal end 64. The pawl also allows the biasing force to be adjusted in increments without any loss of previous gains. Once the desired biasing force has been reached, theset screws 52 may then be tightened to additionally secure theactuator member 60 from rotating. The pawl may be biased in different directions to prevent rotation of theactuator member 60 in either the clockwise or counterclockwise direction as desired. Alternatively, the teeth may be located on theactuator member 60 and the pawl on thebase 24.

Thetensioner 10 is designed to be retrofit on existing conveyorbelt cleaning shafts 16. Thetensioner 10 may also be used to replace an existing tensioner which has proven to be unsatisfactory or otherwise in need of replacement or thetensioner 10 may be added to existing conveyor belt cleaning shafts which were previously not provided with a tensioner. Thetensioner 10 may also be supplied as original equipment with a conveyor belt cleaner mechanism. The tensioner 10 permits quick and easy installation of a tensioner to an existingcleaner shaft 16 without requiring any major modifications to the existing equipment.

Various features of the invention have been particularly shown and described in connection with the illustrated embodiments of the invention, however, it must be understood that these particular arrangements only illustrate and that the invention must be given its fullest interpretation within the terms of the appended claims.

Claims (11)

What is claimed is:

1. A tensioning device for imparting torsional bias to a support shaft which is rotatable with respect to a fixed frame including means for imparting torsional bias to the shaft, said biasing means including a first end, a second end and a center section, said center section extending radially between said first end and said second end; means for connecting said first end of said biasing means to the shaft for conjoint rotation therewith; an actuator member selectively connectable to the fixed frame such that said actuator member is relatively repositionable with respect to the fixed frame; means for connecting said second end of said biasing means to said actuator member; and means associated with said actuator member and the fixed frame for connecting said actuator member to the fixed frame after the torsional biasing force is imparted to the shaft, whereby repositioning of said actuator member is effective to impart a torsional bias to the shaft through said biasing means.

2. The tensioning device of claim 1 wherein said means for connecting said first end of said biasing means to the shaft includes an adapter having a first end and a second end, said first end being adapted for connection to the shaft, said second end adapted for connection to said first end of said biasing means.

3. The tensioning device of claim 2 wherein said second end of said adapter defines a slot through which said center section of said biasing means passes.

4. The tensioning device of claim 1 wherein said center section of said biasing means is thinner than said first end or said second end of said biasing means.

5. The tensioning device of claim 1 additionally including a base connected to the fixed frame and connectable to said actuator member to selectively prevent rotation of said actuator member after a torsional bias is imparted to said shaft.

6. The tensioning device of claim 5 including ratchet means connectable between said base and said actuator member to allow for selective incremental rotational movement of said actuator member with respect to said base in one direction only.

7. The tensioning device of claim 1 additionally including a bushing disposed between the shaft and the fixed frame to absorb vibrations from the shaft.

8. The tensioning device of claim 1 wherein said actuator member comprises a hub, said hub including a slot defined through the outer periphery of said hub, said slot being adapted to allow said center section of said biasing means to pass through said slot.

9. The tensioning device of claim 1 including means for rotating said actuator member to thereby impart a torsional bias to said shaft.

10. The tensioning device of claim 1 wherein said biasing means is operative to impart a torsional bias to said shaft when said actuator member is rotated in either direction of rotation.

11. The tensioning device of claim 1 in which said biasing means includes a resilient elastomeric web extending radially between the shaft and said actuator member.

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